JP2023073702A - battery module - Google Patents

Abstract

To provide a battery module that applies appropriate pressure to a laminate, absorbs the displacement of the pressurized load that accompanies charging and discharging of a stacked battery cells when using a lithium-ion battery, can fix a pressure plate at the end of the stacking direction of the lithium-ion battery stack to a case.SOLUTION: A battery module includes a cell laminate in which a plurality of battery cells are stacked, each having a power generation element and an outer body covering the power generation element, a fastening member that fastens the cell laminate, end plates arranged at both ends of the cell laminate in the stacking direction, a fastening nut that fastens the fastening member and the end plate on the outside of the cell laminate, a stay fastened by the fastening nut, and a case containing the cell laminate, and the cell laminate is fixed to the case by the stay.SELECTED DRAWING: Figure 1

Description

The present invention relates to battery modules.

In order to properly function a battery module that serves as a power source for an electric vehicle or the like, it is necessary to pressurize the stacked battery cells by applying pressure in the stacking direction. In particular, in a solid secondary battery using a solid electrolyte as an electrolyte, it is necessary to apply much higher pressure than in a liquid secondary battery using a liquid electrolyte. As a pressurizing method, there is a method of joining end plates and side plates to both side end surfaces and side surfaces of the stack in a state where the stack is initially pressed from both side end surfaces of the stack of battery cells.

In the pressurization method described above, it is necessary to apply initial pressurization to the laminate that is higher than the target pressure. In addition, there is a problem that the residual load becomes non-uniform because the elastic modulus of the laminated body varies in the lamination direction. Furthermore, as a result of the need for strength and rigidity of the end plates and side plates, there is also the problem that the space for the members increases and the occupancy rate of the battery cells in the battery module decreases. As a pressurizing method other than the above, a technique is disclosed in which a laminate is sandwiched between a pair of pressurizing plates and a connecting rod presses the pair of pressurizing plates (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2008-293771

The technique disclosed in Patent Document 1 is to arrange a plurality of prismatic lithium-ion batteries on the same plane and connect a pair of pressure plates with a central connecting rod and a peripheral connecting rod. The pair of pressure plates are pressed toward each other by tightening screw members attached to both ends of the peripheral connecting rod. However, in the above technology, displacement occurs in the cell stacking direction when the lithium ion battery expands or contracts due to charging and discharging. It becomes difficult to fix the pressure plate to the case.

The present invention has been devised in view of the above, and is capable of suitably pressurizing a laminate and absorbing the displacement of the pressurizing load that accompanies charging and discharging of the stacked battery cells during use of a lithium-ion battery. SUMMARY OF THE INVENTION An object of the present invention is to provide a battery module in which pressure plates at ends in the stacking direction of a lithium-ion battery stack can be fixed to a case.

(1) The present invention provides a cell stack in which a plurality of battery cells are stacked, each having a power generation element and an exterior body covering the power generation element, a fastening member for fastening the cell stack, and the cell stack. end plates arranged at both ends in the stacking direction of the body; fastening nuts for fastening the fastening members and the end plates on the outside of the cell stack; stays fastened by the fastening nuts; and the cell stack. and the cell stack is fixed to the case by the stay.

According to the invention of (1), it is possible to provide a battery module that can absorb displacement due to expansion and contraction of the cell stack by means of the stay.

(2) The battery module according to (1), wherein the rigidity of the stay in the stacking direction is lower than the rigidity of the stay in a direction perpendicular to the stacking direction.

According to the invention of (2), displacement due to expansion and contraction of the cell stack can be preferably absorbed by the stay.

(3) The battery module according to (1) or (2), wherein the stay has a first inclined portion inclined in a downward widening direction when viewed from the stacking direction.

According to the invention of (3), displacement due to expansion and contraction of the cell stack can be preferably absorbed by the stay.

(4) Any one of (1) to (3), wherein the stay has a second inclined portion that slopes downward from the fastening portion with the fastening nut toward the outside in the stacking direction of the cell stack. Battery module as described.

According to the invention of (4), displacement due to expansion and contraction of the cell stack can be preferably absorbed by the stay.

(5) Any one of (1) to (4), wherein a plurality of the fastening members are arranged, and the stay has a plurality of holes through which part of the fastening members are inserted, and is integrally formed. The battery module described in .

According to the invention of (5), the rigidity of the stay can be designed more precisely, and the reliability of the battery module can be improved.

1 is a partial cross-sectional view showing a battery module according to a first embodiment of the invention as viewed from the side; FIG. FIG. 2 is an exploded view showing the structure of the battery module of FIG. 1; FIG. 3 is an enlarged view of a main part of FIG. 2; FIG. 6 is a partial cross-sectional view showing a battery module according to a second embodiment of the present invention as viewed from above; FIG. 5 is a partial cross-sectional view showing the battery module of FIG. 4 in a side view; FIG. 5 is a diagram of the battery module of FIG. 4 viewed from one stacking direction side; FIG. 5 is a view of the stay of the battery module in FIG. 4 as viewed from one stacking direction side; FIG. 8 is a side view of a stay of the battery module of FIG. 7; FIG. 8 is a view of the overall configuration of the stay of the battery module of FIG. 7 viewed from one stacking direction side; FIG. 8 is a diagram showing a modification of the stay of the battery module of FIG. 7; FIG. 11 is a side view of the stay of FIG. 10;

(First embodiment)
A battery module according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. In each drawing shown below, the same reference numerals are given to the same parts and corresponding parts.

[Cell laminate]
A battery module 10 according to the first embodiment, as shown in FIG. 11b. The power generation element 2 is, for example, a solid battery in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are repeatedly laminated in this order. In the following description, the power generation element 2 will be described as a solid battery, but the power generation element 2 may be an electrolytic solution system battery including a liquid electrolyte. The battery module 10 has a fastening member 4, a central fixing member 5, an end plate 6, a pressure plate 7, a stay 8, and a fastening nut f1 in addition to the above.

As materials for forming the positive electrode layer, the solid electrolyte layer, and the negative electrode layer as the power generation element 2, known materials for forming a solid battery can be used.

The exterior body 3 accommodates the power generation element 2 inside. Although the exterior body 3 is not particularly limited, it is preferably a laminate film. By configuring the outer package 3 with a laminate film, the volume of the outer package 3 can be reduced, and the energy density of the battery module can be improved. A laminate cell has a multi-layer structure in which, for example, a metal layer made of aluminum, stainless steel (SUS), or the like is laminated with a heat-sealable resin layer such as polyolefin on the outside. A metal can can also be used as the exterior body 3 .

A plurality of battery cells 1 are stacked in the same direction (stacking direction L1 shown in FIG. 1) as the stacking direction of the electrode layers constituting the power generation element 2 to form cell stacks 11a and 11b. The cell stacks 11a and 11b are held by being pressed by end plates 6 from both end sides in the stacking direction L1.

As shown in FIG. 2 , in the plurality of battery cells 1, at the central portion of the cross section in the vertical direction along the stacking direction L1, first through holes are formed in the direction of penetrating each electrode layer constituting the power generation element 2. A hole h1 (hereinafter sometimes simply referred to as "through hole h1") is provided. The through hole h1 is a hole that penetrates the battery cell 1 together with the exterior body 3 . Although the shape of the through hole h1 is not particularly limited, it preferably has a circular cross-sectional shape similar to the cross-sectional shape of the fastening member 4, which will be described later. As a method for forming the through holes h1, for example, a through hole is formed in each of the electrode layers and the solid electrolyte layers constituting the power generation element 2 to form a laminate, the laminate is enclosed in the exterior body 3, and the above The exterior bodies 3 are joined together at locations corresponding to the through holes by welding the laminate film, and a through hole slightly smaller than the through hole is formed in the exterior body 3 on the inner peripheral side of the through hole by punching or the like. It can be formed by

A plurality of battery cells 1 are arranged so that the through holes h1 communicate with each other, and a fastening member 4 for fastening the cell stacks 11a and 11b is arranged in the through holes h1. The pair of end plates 6 are fastened by the fastening member 4 in a direction to narrow the distance between them. As a result, the cell laminates 11a and 11b can be pressurized without being initially pressurized (prepressurized).

[Fastening member]
The fastening member 4 includes a shaft portion forming a main body, male screw portions 41 formed at both ends of the shaft portion, an enlarged diameter portion 42 forming a part of the shaft portion and formed in the central portion in the axial direction, It has a detent portion 43 arranged between the male screw portion 41 and the shaft portion. The expanded diameter portion 42 is arranged in a second through hole h2 of the central fixing member 5, which will be described later. The fastening members 4 have their shafts inserted through the through holes h1 of the cell stacks 11a and 11b, and the male screw portions 41 are connected to the end plates 6, pressure plates 7 and stays at both ends of the cell stacks 11a and 11b. 8 are extended from holes h3, h4, and h5 respectively provided in 8, and are screwed to the fastening nut f1. The cross-sectional shape of the fastening member 4 is preferably circular from the viewpoint of making the cross-sectional stress uniform.

By inserting the fastening member 4 into the through hole h1 provided in the central portion of the stacking surfaces of the cell stacks 11a and 11b and pressurizing the cell stacks 11a and 11b using a pair of end plates 6 and fastening nuts f1, , the surface pressure applied to the cell laminates 11a and 11b can be made uniform. In addition, an outer frame for fixing the cell stack is not required, and the volume ratio of the power generation elements 2 in the battery module 10 can be improved, so the energy density of the battery module 10 can be improved. In the present invention, the fastening member 4 is not limited to one that is inserted through the through hole h1 provided in the central portion of the stacking surface of the cell stack. The fastening member 4 may be arranged at a location other than the central portion on the stacking surface of the cell stack.

As shown in FIG. 1, the anti-rotation portion 43 is arranged inside the hole h3 formed in the end plate 6 near the fastening nut f1. The anti-rotation portion 43 is, for example, a member having a polygonal shape or a sawtooth shape when viewed in cross section. The anti-rotation portion 43 may be formed integrally with the fastening member 4 , or may be configured as a separate member from the fastening member 4 and fixed to the fastening member 4 .

The anti-rotation portion 43 is fitted into a hole h3 having an inner surface shape corresponding to the cross-sectional shape of the anti-rotation portion 43, which is formed in the end plate 6, for example, so that the torsional stress in the axial direction of the fastening member 4 is reduced. It has the function of receiving. As a result, the torsional stress generated when the male threaded portion 41 is screwed to the fastening nut f1 is transmitted only to the male threaded portion 41 of the fastening member 4 and the anti-rotation portion 43. is not transmitted to the internal side of the Therefore, loosening of the fastening nut f1 during use of the battery module 10 can be prevented for a long period of time. Further, by tightening the fastening nut f1, a larger axial force can be applied to the fastening member 4. As shown in FIG. In addition to the above, it is possible to precisely adjust the surface pressure applied to the cell stacks 11a and 11b by adjusting the tightening degree of the fastening nut f1.

The diameter of the axial section of the shaft portion 44 of the fastening member 4 shown in FIG. 2 can be designed according to the surface pressure applied to the cell stacks 11a and 11b. By reducing the diameter, the stress per unit area applied to the shaft portion 44 increases, so it becomes possible to reduce the elastic modulus that maintains the distance between the end plates 6 in the direction of compression. It is possible to reduce the variation width of the surface pressure applied to 11b.

[Central fixing member]
The central fixing member 5 is a member arranged between the plurality of battery cells 1 and, as shown in FIG. 1, is a member arranged in the center of the battery module 10 in the stacking direction L1. The surface pressure applied to the cell stacks 11a and 11b is made uniform in the stacking direction L1 by the central fixing member 5. As shown in FIG. Since the central fixing member 5 receives only a compressive force in the stacking direction L1, it can be made of a lightweight metal such as aluminum.

The central fixed member 5 is provided with a second through hole h2 (hereinafter sometimes simply referred to as “through hole h2”) in which the enlarged diameter portion 42 of the fastening member 4 is arranged. As shown in FIG. 2, the central fixing member 5 is arranged so that the through hole h2 communicates with the through hole h1. The through hole h2 may be fixed on a plane perpendicular to the axial direction by means of spigot fixing or the like to the expanded diameter portion 42 . Thereby, the central fixing member 5 and the fastening member 4 can be positioned and fixed, and the central fixing member 5 can be easily arranged in the center of the battery module 10 in the stacking direction L1.

[end plate]
The end plates 6 are a pair of members arranged at both ends in the stacking direction L1 of the cell stacks 11a and 11b. As shown in FIG. 2, the end plate 6 is formed with a hole h3 through which the fastening member 4 can be inserted. The fastening member 4 is inserted through the hole h3 and fastened with the fastening nut f1, so that the end plate 6 holds the cell stacks 11a and 11b under pressure.

The end plate 6 has an inclined portion 61 and a load point 62, as shown in FIG. The load point 62 is a surface continuous with the inclined portion 61 and substantially perpendicular to the stacking direction L1. The end plate 6 abuts the pressure plate 7 at a plurality of load points 62 . As a result, the surface pressure applied from the end plate 6 to the cell stacks 11a and 11b is made uniform with respect to the stacking surfaces.

[Pressure plate]
The pressure plate 7 is a pair of members that are fastened together with the end plate 6 by fastening nuts f1. The pressure plates 7 are arranged outside the end plates 6 in the stacking direction L1 at both ends of the cell stacks 11a and 11b in the stacking direction L1. The pressure plate 7 is an elastically deformable member, such as a leaf spring-like member made of metal. As shown in FIG. 2, the pressure plate 7 is formed with a hole h4 through which the fastening member 4 can be inserted. The fastening member 4 is inserted through the hole h4 and fastened with the fastening nut f1, whereby the axial force generated by tightening the fastening nut f1 is transmitted to the end plate 6 via the pressure plate 7.

The pressure plate 7 has an inclined portion 71 and a load point 72, as shown in FIG. The inclined portion 71 is a surface inclined along the inclined portion 61 . The load point 72 is a surface continuous with the inclined portion 71 and substantially perpendicular to the stacking direction L1.

[Stay]
The stay 8 is a pair of members that are fastened together with the end plate 6 and the pressure plate 7 by fastening nuts f1. The stay 8 is a member for fixing the cell laminates 11a and 11b. The stays 8 are arranged outside the pressure plate 7 in the stacking direction L1 at both ends of the cell stacks 11a and 11b in the stacking direction L1. As shown in FIG. 2, the stay 8 is formed with a hole h5 through which the fastening member 4 can be inserted. The fastening member 4 is inserted through the hole h5 and fastened with the fastening nut f1. By fixing the stay 8 using the fastening member 4, the installation space for the stay 8 and the number of parts can be reduced. Details of the configuration of the stay 8 will be described in a second embodiment below.

(Second embodiment)
Next, a second embodiment of the invention will be described with reference to FIGS. 4 to 9. FIG. In the following description, the same reference numerals may be given to the drawings for the same configuration as in the first embodiment, and the description thereof may be omitted.

FIG. 4 is a top view of the battery module 100 according to the second embodiment. The battery module 100 is obtained by combining the battery modules 10 into a larger battery module. As shown in FIGS. 4 and 5, in the plurality of battery cells 1a, a plurality of holes are formed in the central portion of the cross section in the vertical direction along the stacking direction L1, and a plurality of fastening members 4 (in this embodiment) are formed. In the form, three) are inserted and arranged. The number of fastening members 4 to be arranged is not limited to the above, and may be, for example, two or four. As shown in FIGS. 5 and 6, the battery module 100 includes a case 9 that houses a stack of battery cells 1a.

The central fixing member 5a according to this embodiment has a plurality of through holes h2 through which the fastening members 4 are inserted. Further, the central fixing member 5a has a connection portion 51 with the case 9. As shown in FIG. A fastening bolt f<b>2 is screwed into the connecting portion 51 to connect the central fixing member 5 a and the case 9 . Thereby, the rigidity of the stack of battery cells 1a can be further increased.

As shown in FIG. 6, three pressure plates 7 according to this embodiment are arranged in a direction L2, which is a direction perpendicular to the stacking direction L1. In this embodiment, four load points 72a, 72b, 72c, and 72d at which the pressure plate 7 contacts the end plate 6 are arranged at symmetrical positions with respect to the fastening nut f1.

[Stay]
As shown in FIGS. 6 and 7, the stay 8a according to this embodiment has connecting portions 83 with the case 9 at both ends in a direction L2 orthogonal to the stacking direction L1 and/or between the fastening members 4. As shown in FIGS. A fastening bolt f<b>3 is screwed into the connecting portion 83 to connect the stay 8 a and the case 9 . Thereby, the rigidity of the stack of battery cells 1a can be further increased. Further, the stay 8a is made of an elastically deformable member, and the rigidity in the stacking direction L1 is set lower than the rigidity in the direction perpendicular to the stacking direction L1. Thereby, the stay 8a can absorb the displacement caused by the expansion and contraction of the stack of the battery cells 1a. Therefore, even though the battery cells 1a expand and contract when the battery module 10 is used, the pressure plate 7 can be fixed to the case 9 via the stays 8a.

FIG. 7 is a view of part of the stay 8a arranged on the stack end side of the battery module 100 from the stacking direction L1 from the same viewpoint as FIG. As shown in FIG. 7, the stay 8a has a first inclined portion 81 inclined in a downward widening direction when viewed from the stacking direction L1. Further, as shown in FIG. 8, the stay 8a has a second inclined portion 82 inclined downward in the stacking direction L1 from the hole h5, which is a fastening portion with the fastening nut f1. With the above configuration, the stay 8a is flexurally deformed in the stacking direction L1, thereby absorbing displacement accompanying expansion and contraction of the stack of the battery cells 1a. On the other hand, the rigidity with respect to the stacking surface of the battery cells 1a is high, and the stack of the battery cells 1a can be preferably fixed.

FIG. 9 is an overall view of the stay 8a used in the battery module 100 from the same viewpoint as in FIG. The stay 8a is not provided individually according to the numbers of the fastening members 4 and the holes h5, but as shown in FIG. is preferred. By integrally molding the stay 8a, the connection portion 83a with the case 9 provided between the holes h5 can be made into a single piece. Therefore, compared to the case where the stays 8a are individually provided and the connecting portions 83a are overlapped with each other and tightened together with the fastening bolts f3, no step occurs in the connecting portions 83a. Therefore, the rigidity of the stay 8a for absorbing the displacement caused by the expansion and contraction of each cell stack can be designed more precisely, so that the reliability of the battery module 100 can be improved. Also, the number of parts of the battery module 100 can be reduced, and the assembling workability can be improved. Further, by inserting the fastening member 4 through the plurality of holes h5 and fastening with the fastening nut f1, the same effect as the rotation prevention portion 43 of the fastening member 4 can be obtained. The fastening member 4 can be constructed.

(Third embodiment)
FIG. 10 is a view of part of the stay 8b according to the third embodiment viewed from the same viewpoint as in FIG. The stay 8b can be applied to battery modules similar to the battery module 100 to which the stay 8a is applied.

Like the stay 8a, the stay 8b has connecting portions 83 with the case 9 at both ends in the direction L2 orthogonal to the stacking direction L1 and/or between the fastening members 4. As shown in FIG. A fastening bolt f<b>3 is screwed into the connecting portion 83 to connect the stay 8 b and the case 9 . Moreover, as shown in FIG. 10, it has the 1st inclination part 81a. FIG. 11 is a view of the stay 8b viewed from the stacking direction L1, as in FIG. The stay 8b has a second inclined portion 82 like the stay 8a.

The stay 8b has a hole h6 as shown in FIG. By providing the hole h6 in the stay 8b, it is easy to design the rigidity of the stay 8b in the stacking direction L1. This is because the rigidity of the stay 8b in the stacking direction L1 can be adjusted by adjusting the size of the hole h6. In addition to the above, since the stay 8b has the hole h6, it is possible to increase the allowable amount of deflection in the stacking direction L1. Therefore, it is possible to more preferably absorb the displacement caused by the expansion and contraction of the stack of battery cells 1a. Although the shape of the hole h6 in FIG. 10 has a substantially rectangular opening, the shape of the hole h6 is not particularly limited.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified as appropriate.

In the above embodiment, the anti-rotation portion 43 has been described as fitting into the hole h3 formed in the end plate 6 and having an inner surface shape corresponding to the cross-sectional shape of the anti-rotation portion 43 . Not limited to the above. The anti-rotation portion 43 may be provided at the end of the male threaded portion 41 to fix the end of the male threaded portion 41 .

In the above-described embodiment, the stays 8 and 8a are described as having a hole h5 through which the fastening member 4 can be inserted and fastened with the fastening nut f1. Not limited to the above. The stay in the present invention may be connected to the pressure plate at one or more points.

REFERENCE SIGNS LIST 10, 100 battery module 1, 1a battery cell 11a, 11b cell stack 2 power generating element 3 exterior body 4 fastening member 43 anti-rotation portion 5, 5a central fixing member 51 connecting portion 6 end plate 8 stay 81 first inclined portion 82 second 2 inclined portion 9 case f1 fastening nut h1 first through hole h2 second through hole h5 hole portion L1 stacking direction

Claims (5)

a cell stack in which a plurality of battery cells are stacked, each having a power generation element and an outer body covering the power generation element;
a fastening member that fastens the cell stack;
end plates disposed at both ends of the cell stack in the stacking direction;
a fastening nut for fastening the fastening member and the end plate on the outside of the cell stack;
a stay fastened by the fastening nut;
a case that accommodates the cell stack,
The battery module, wherein the cell stack is fixed to the case by the stay. 2. The battery module according to claim 1, wherein rigidity of said stay in said stacking direction is lower than rigidity of said stay in a direction orthogonal to said stacking direction. 3. The battery module according to claim 1, wherein said stay has a first inclined portion inclined in a downward widening direction when viewed from said stacking direction. The battery module according to any one of claims 1 to 3, wherein the stay has a second sloped portion that slopes downward toward the outside in the stacking direction of the cell stack from a fastening portion with the fastening nut. A plurality of the fastening members are arranged,
5. The battery module according to claim 1, wherein said stay has a plurality of holes through which a part of said fastening member is inserted, and is integrally formed.

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